This Phase II project focuses on remote physiologic status monitoring of personnel wearing personal protective equipment (PPE) through self-contained breathing apparatus (SCBA)-based oximetry systems, radio-telemetry and processing software for the development of an adjunct safety device addressing the prevalent problem of volitional fatigue experienced by fire fighters combating structural fires. An integrated SCBA-based monitoring system capable of unencumbered assessment of the physiological status of fire fighters under exertive working conditions would greatly serve to reduce fire fighter line-of-duty deaths attributed to heart attacks and other manifestations of physiologic stress and offers a valuable research tool for studying exertion-related heat stress in workers wearing PPE. During Phase I of this effort, an initial prototype was built and validated that acute changes in the DC, or non-pulsatile component of the oximetry waveform, correspond to physiologic fatigue in working fire fighters. The proposed Phase II project further develops the SCBA-based monitoring system, and focuses on refining and building the next generation prototype, defining the physiologic reactions to exertion as measured by the oximetry waveforms to establish monitoring parameters and alarm thresholds, and developing and evaluating algorithms based on physiologic correlations against changes in DC oximetry. Once the units are fabricated, they will be evaluated under realistic field conditions to demonstrate hardness, functionality, and system reliability. Research and testing to date suggests that this system will effectively provide reliable and non-invasive identification of the onset of volitional fatigue and facilitate timely fire fighter self-rescue. [unreadable] [unreadable]